Kepa is off contract at the end of the season and is a target for Real.
Nacho told Quatro: "He is a great goalkeeper and has a very good career. Last year he played good games. He's playing at a spectacular level.
"Real Madrid always goes for the best and if the club is committed to a player, the players of the staff will be there to support and back him."
While his deal expires in June, Real could yet sign Kepa in January with his contract carrying a €20m buyout clause.